1. Field of the Invention
The present invention relates to an apparatus for changing the width of a gap between an end of a rail section and an adjacent end of a longitudinally succeeding rail section of a rail fastened to ties by fastening elements, two of the rails and the ties constituting components of a track and each rail section comprising a vertically extending web and a rail head, the gap being reduced by tensioning or longitudinally extending the rail section after the fastening elements fastening the rail section to the ties have been loosened. The apparatus comprises two longitudinally spaced beams extending transversely to the track rails, a pair of clamping members mounted on each transverse beam for pivoting about parallel vertical axes at respective sides of the rail sections of the rail and having cooperating clamping jaws for engaging the rail sections between the clamping members upon pivoting thereof, the pairs of clamping members being longitudinally spaced from each other, and hydraulic drives interconnecting the clamping members at each side of the rail sections of the rail.
2. Description of the Prior Art
British patent No. 1,294,216, published Oct. 25, 1972, discloses a ring-shaped structural rail tensioning unit of this general type and comprising two longitudinally spaced clamping heads interconnected by tie members extending above and below the rail for rotation about vertical axes. The clamping heads have clamping jaws for engagement with the rail web and are connected by short bell-crank levers to hydraulic drives and tensioning members extending in the direction of the rail. When the two hydraulic drives are operated by a manually actuated hydraulic fluid pump, the clamping heads are pivoted towards the rail and the clamping jaws are pressed against the rail web. Subsequently, the two adjacent rail section ends are longitudinally extended towards each other to reduce the gap therebetween to the desired distance However, the two rail section ends cannot be centered with respect to each other.
European patent application No. 132,227, published Jan. 23, 1985, discloses a mechanism for the alignment of two adjacent rail section ends and flash butt-welding the aligned rail section ends. The mechanism comprises a rigid frame comprised of two elongated beams extending parallel to the rail and four cross beams rigidly interconnecting the elongated beams. Casings are arranged at the longitudinal ends of the frame below and above the frame and the casings are displaceable towards each other by hydraulic drives. Tensioning tongs comprising two clamping jaws are arranged at each end of the mechanism and a transversely extending cylinder actuates the clamping jaws for engagement with the interposed rail web. This mechanism is costly and complex, due to the rigid frame and the numerous hydraulic drives.
Another rail tensioning mechanism including clamping heads interconnected by hydraulic drives has been disclosed in European patent application No. 253,634, published Jan. 20, 1988. Other hydraulically operated rail tensioning devices for reducing the gap between adjacent rail section ends are disclosed in European patent No. 16,664, published Jan. 19, 1983, and German patent application No. 2,830,006, published Jan. 25, 1979.
U.S. Pat. No. 4,938,801, dated Jan. 8, 1991, describes another rail tensioning apparatus of the first-described type, wherein the two pairs of clamping members are so spaced longitudinally that the resultant ring-shaped rail tensioning mechanism including the interconnecting hydraulic drives provides sufficient space to accommodate a flash butt-welding head. In this manner, even relatively heavy rail sections with substantial gaps between adjacent ends thereof may be pulled together for flash butt-welding.